1. Field of the Invention
Aspects of the present invention relate to a power supplying device, and more particularly, to a fuel cell system and a method of operating the same.
2. Description of the Related Art
There are many types of fuel cells. Fuel cells can be divided into direct methanol fuel cells (DMFCs), which directly use methanol, and proton exchange membrane fuel cells (PEMFCs).
A DMFC produces power in a process in which electrons and hydrogen ions, generated at an anode of a membrane electrode assembly (MEA), are moved to a cathode of the MEA and react with oxygen. The electrons and hydrogen ions are generated by reaction of methanol supplied from a cartridge and water, at the anode of the MEA. Fuel is continuously supplied from the cartridge to the MEA while the DMFC is operated. Accordingly, when the operation of the DMFC is stopped, or there is no load connected to the DMFC, the fuel is no longer supplied, but residual fuel may remain between the cartridge and the MEA and also on the inside of the MEA.
If the DMFC is a passive fuel cell, it is very difficult to completely remove the residual fuel when the DMFC stops operating, thereby requiring an additional method to remove the residual fuel. If the residual fuel is not removed from the MEA, the MEA is continuously exposed to the residual fuel, such that the MEA, specifically, a filter and electrodes installed in the MEA, may be structurally damaged. In particular, if the fuel is highly concentrated, damage to the MEA may be more severe. Also, when the residual fuel exits from a carbon dioxide (CO2) outlet, such a discharge may violate the safety standards of the International Standardization Organization (ISO).
If the DMFC has an active component, the residual fuel may be removed to some extent using the active component. However, additional power is necessary to operate the active component, and as such, it is difficult to completely remove the residual fuel from the MEA.
Many attempts have been made to solve the problems posed by residual fuel in a DMFC. For example, there is a method of consuming the residual fuel in the DMFC, by connecting an additional load to the DMFC. However, since this method necessarily requires the additional load, the method becomes complex, costly, and time consuming.